JP2014097450A - Evaporator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporator suppressing the temperature rise of the bottom part of an evaporator for a long period and achieving reduction of life cycle costs.SOLUTION: An evaporator 101 comprises a capture container 204 arranged in the bottom part of the evaporator 101 in such a way as to avoid a free convection passage for a solution in the evaporator 101, an induction pipe 201 arranged so as to face the bottom part of the evaporator 101 and provided with an ejector 202 in the halfway and an injection tip at the tip, a first suction pipe arranged in a part of the capture container 204 and sucking the solution in the evaporator 101 and a second suction pipe arranged between the capture container 204 and the ejector 202 and guiding the solution in the capture container 204 to the ejector 202. In the ejector 202, the main flow F2 introduced into the induction pipe 201 and a capture flow F3 flowing from the first suction pipe through the capture container 204 and the second suction pipe are joined and jetted from the injection tip at the tip of the induction pipe 201 toward the bottom part of the evaporator 101 as an agitation flow.

Description

  The present invention relates to an evaporator for concentrating or reducing the volume of a solution by heating and evaporating the solution.

  In a chemical plant or the like, an evaporator is used for the purpose of concentration or volume reduction of the solution. For example, in a food-related facility, an evaporator is used in a scene where a food solution is concentrated or waste liquid from a chemical plant is reduced (volume reduction). Here, for concentration or volume reduction, a heater or the like is installed outside the evaporator to heat the solution inside.

  Due to the external heating in the evaporator, the density of the solution inside decreases and the inside of the evaporator rises. On the other hand, in the vicinity of the liquid surface of the solution, the heat in the vicinity of the liquid surface is removed due to the evaporation of the solution, the density increases, and the inside of the evaporator is lowered. As a result, in the evaporator, the solution is evaporated and concentrated or reduced in volume while generating natural convection in which the solution rises and falls.

  Depending on the type of solution, the solution may contain a component that precipitates as a solid phase (hereinafter simply referred to as a solid phase). If a component that precipitates as a solid phase is dissolved in the solution, the solid phase may be deposited at an unspecified position in the evaporation process. Of the precipitated solid phase, the solid phase having a density higher than that of the solution is precipitated and deposited on the bottom of the evaporator. Since the solid phase that has settled and hinders the solution flow at the bottom of the evaporator, if there is heating from the bottom of the evaporator, the amount of heat removed from the heat transfer surface at the bottom of the evaporator that is in contact with the solid phase decreases, and the evaporator This results in an increase in the bottom heat transfer surface temperature.

  As the temperature rises, the corrosion potential of the heat transfer surface structure increases. For this reason, in an evaporator using a solution containing a solid phase, it is necessary to take measures such as increasing the thickness of the bottom of the evaporator in the design stage from the viewpoint of the corrosion potential of the heat transfer surface structure material.

  Conventionally, several methods are known as countermeasures for the above-described problems in the evaporator. Patent Document 1 proposes a natural circulation evaporator that continuously evaporates a low-boiling component that does not precipitate solid particles when the liquid to be treated is slurry.

  Patent Document 2 uses a porous filtration medium as a technique for separating a solid in a liquid.

  Patent Document 3 proposes a sedimentation separator using a transfer ejector and a sedimentation tank as a method for recovering the particles of the particulate mixed waste stream in the catcher tank. Further, as a method for preventing sedimentation of particles in the particle mixed waste liquid in the catcher tank, it is known to stir by a waste liquid jet by an ejector.

JP-A-11-333201 Japanese Examined Patent Publication No. 3-49607 JP 2001-260030 A

  In the evaporator according to the present invention, it is assumed that there is heating from the bottom of the evaporator and solid phase precipitation occurs. In the evaporator according to the present invention, the precipitated solid phase is recovered, and at this time, the natural convection inside the evaporator is not hindered, and high efficiency and high availability are achieved.

  For these specifications, for example, it is inappropriate to use an evaporator with no solid particle precipitation as shown in Patent Document 1. In the case of Patent Document 1, only a low boiling point component is a target for evaporation, and a component having an arbitrary boiling point may not be evaporated.

  It is necessary to consider that the following problems occur incidentally in an evaporator with solid phase precipitation that is a prerequisite of the present invention. First, the solid phase deposited on the bottom of the evaporator obstructs the flow of the bottom of the evaporator, reducing the amount of solution reaching the bottom of the evaporator. When there is heating from the outside of the evaporator, this causes a temperature rise at the bottom of the evaporator and increases the corrosion potential. Therefore, it is necessary to take measures such as increasing the corrosion allowance in advance.

  In addition, in order to suppress the amount of solid phase deposited on the bottom of the evaporator, when a structure or the like is inserted into the evaporator, it is necessary to have a structure that does not inhibit natural convection. When natural convection is hindered, the amount of solution flowing into the solid phase deposition layer at the bottom of the evaporator can be reduced, raising the temperature at the bottom of the evaporator and increasing the corrosion potential.

  Furthermore, when a conventional collecting member (for example, Patent Document 2) is used in an evaporator for solid-phase collection, it is necessary to replace or wash the filter to prevent clogging. There is a risk of lowering the capacity factor.

  Furthermore, it is necessary to consider the means for collection to the outside. In an evaporator equipped with a particle recovery device (for example, Patent Document 3) outside, it is necessary to additionally install a transfer facility and a recovery container, which may increase the size of the facility and increase the facility cost.

  In Patent Document 3, a stirring mechanism is provided, the solid phase deposited on the bottom of the evaporator by stirring is diffused, and heat removal from the bottom of the evaporator is promoted. However, since the stirred solid phase is deposited again on the bottom of the evaporator, it is always necessary to stir. Moreover, there is a possibility of obstructing natural convection of the solution inside the evaporator by constantly stirring.

  From the above, the object of the present invention is to achieve life cycle cost reduction by suppressing the temperature rise at the bottom of the evaporator and reducing the evaporator corrosion potential for a long time without reducing the evaporator operation rate. It is to provide an evaporator that can.

  From the above, the present invention heats the internal solution with a heater or the like provided on the wall surface, evaporates the solution and concentrates it, and in the evaporator where the solid phase is precipitated by concentration of the solution, at the bottom of the evaporator, A collection container arranged so as to avoid a natural convection flow path due to the solution in the evaporator, a guide pipe arranged toward the bottom of the evaporator, an ejector in the middle, and an injection port at the tip, and a trap A first suction pipe that is provided in a part of the collection container and sucks the solution in the evaporator, and a second suction pipe that is provided between the collection container and the ejector and guides the solution in the collection container to the ejector. The ejector joins the main flow introduced into the guide pipe and the collected flow obtained from the first suction pipe through the collection container and the second suction pipe, and the ejection port at the tip of the guide pipe It is characterized by being ejected as a stirring stream from the bottom of the evaporator That.

  With the above-described configuration of the present invention, the heat removal at the bottom of the evaporator due to the solid phase agitation and the amount of solid phase to be re-precipitated are reduced, and the temperature at the bottom of the evaporator can be increased for a long time without reducing the evaporator operation rate. By suppressing and reducing the evaporator corrosion potential, life cycle cost reduction can be achieved.

The figure which shows the basic whole structure of the evaporator internal device which concerns on Example 1 of this invention. The figure for demonstrating the phenomenon which arises in an evaporator. The figure for demonstrating the equipment arrangement | positioning in an evaporator, and the moving direction of the fluid for solid-phase collection | recovery. The figure which showed three-dimensionally the piping structure in an evaporator. The figure which shows the cross-sectional example of a collection container and the solid-phase suction pipe connected with this. The schematic diagram of the collection container which concerns on Example 2 of this invention. The schematic diagram of the collection container which concerns on Example 3 of this invention. The schematic diagram of the collection container which concerns on Example 4 of this invention.

  The evaporator according to the embodiment of the present invention will be described in detail with reference to examples and drawings as appropriate. Here, a mechanism for stirring and collecting the solid phase generated along with evaporation and deposited on the bottom of the evaporator will be described as an example, but the target to be collected is not limited to the solid phase but exists in the solution. Impurities may be used and their size is not limited. The heating of the evaporator will be described by taking an external heater that heats the entire evaporator as an example, but the arrangement and shape of the heater are not limited to this (including the case of heating only from the bottom of the evaporator). For convenience of drawing, the evaporator is described in an axial section, and details of piping and the like are omitted.

  A phenomenon occurring in the evaporator can be described with reference to FIG. First, the evaporator can be circular, square or any other shape, but has a function as a tank for storing the solution. Therefore, the evaporator 101 is installed in the vertical axis direction. An external heater 102 is provided outside the evaporator to heat the solution 103 inside the evaporator.

  The solution 103 in the evaporator generates buoyancy and rises due to the density of the solution being reduced by heating the wall surface from the outside of the evaporator. Further, the solution evaporates at the liquid surface 106, heat is taken away from the solution by evaporation, and the density of the solution in the vicinity of the liquid surface increases, so that a downward flow is generated. In FIG. 2, a stable natural convection 104 is generated in which an upward flow is generated in the vicinity of the inner wall of the evaporator 101 as a heating surface and a downward flow is generated in the center of the evaporator. The solution flows along the bottom of the evaporator where the natural convection 104 reversely shifts from the downward flow at the center of the evaporator to the upward flow of the wall surface, thereby removing heat from the bottom of the evaporator. Also, the inner wall of the evaporator is removed by the upward flow near the wall surface.

  The evaporation process proceeds while maintaining the natural convection 104, but when the solution exceeds the saturation concentration, the solid phase 105 is deposited at an unspecified position in the solution. When the density of the solid phase 105 is larger than that of the solution, it settles and finally deposits on the bottom of the evaporator 101. The deposited solid phase 105 becomes a resistance to the flow of the natural convection 104. As a result, the solution due to the downward flow does not reach the bottom of the evaporator, and heat removal due to natural convection is hindered.

  At this time, since the bottom of the evaporator 101 is heated, the temperature of the bottom of the evaporator rises. In general, since the corrosion potential tends to increase as the temperature rises, when the temperature at the bottom of the evaporator 101 rises, the corrosion potential of the evaporator increases, and measures such as increasing the corrosion allowance in advance are required.

  In addition, in order to prevent an evaporator temperature rise, a stirring mechanism can also be provided. However, by stirring the inside of the evaporator, the solid phase 105 deposited on the bottom of the evaporator diffuses, but the diffused solid phase 105 is deposited again on the bottom of the evaporator 101 over time, so it is necessary to constantly stir, There will be a cost.

  Thus, in the evaporator, heating by the external heater 102, natural convection 104, and precipitation and precipitation of the solid phase 105 proceed simultaneously as shown in FIG. Therefore, the present invention proposes the equipment arrangement of FIG. 3 and the moving direction of the solid phase recovery fluid that can effectively collect and recover the solid phase 105 without interfering with the natural convection 104. The arrangement of the equipment in the evaporator and the moving direction of the solid phase recovery fluid will be described with reference to FIG.

  FIG. 3 shows the same evaporator cross section as in FIG. 2, but here the collection container 204 is installed at a position that does not interfere with the natural convection 105 as the first point. The position that does not interfere with the natural convection 104 is a portion where the convection between the upflow and the downflow is relatively small, and as a result, the collection container 204 is preferably formed in a donut shape.

  As a second point, in order to stir the solid phase deposited on the bottom of the evaporator, a stirring flow F1 is given from the upper part of the evaporator to the downstream. The stirring flow F1 is formed such that the main flow F2 entrains the collection flow F3.

  As a third point, in order to collect the solid phase deposited on the bottom of the evaporator, the collected flow F3 joins the main flow F2 from the bottom of the evaporator via the collection container 204, and in this process, the collected flow F3. The solid phase sucked up by is accumulated in the collection container 204.

  As a fourth point, a recovery route F4 is formed to recover the solid phase deposited on the bottom of the evaporator.

  Hereinafter, a description will be given of the equipment configuration for obtaining the equipment layout and the moving direction of the solid phase recovery fluid in FIG. FIG. 1 shows a basic overall configuration of the device. The specific configuration or modified configuration of the device shown in FIG. 1 will be described sequentially with illustrations.

  In FIG. 1, the collection container 204 installed at a position that does not interfere with the natural convection 104 at the first point is disposed in the vicinity of the bottom of the evaporator and is formed in a donut shape as shown in FIG. FIG. 4 is a three-dimensional view of the piping configuration in the evaporator.

  In FIG. 1, the stirring flow F1 from the upper part of the evaporator for stirring the solid phase deposited on the bottom of the evaporator described as the second point from the upper part to the downstream of the evaporator is a solid-phase stirring fluid induction pipe 201 and an ejector. 202 and the stirring nozzle 203 are realized. FIG. 4 shows a guide tube 201, an ejector 202, and a stirring nozzle 203. The stirring nozzle 203 is formed at the tip thereof, and an injection port for injecting the stirring flow F <b> 1 to the deposited solid phase. 301 is formed. The stirring nozzle 203 forms a part of the guide tube 201.

  In FIG. 1, the configuration for collecting the solid phase deposited on the bottom of the evaporator described as the third point is as follows. Here, in order to join the collection flow F3 from the bottom of the evaporator to the main flow F2 via the collection container 204, a solution including a solid phase is provided from a part of the collection container 204 provided with a solid phase suction pipe 205. Inhale. Further, by connecting a solution suction pipe 206 provided at another part of the collection container 204 to the ejector 202, the solution is joined to the main flow F2 as a collection flow F3. As described above, the collection flow F3 is a fluid driven by the main flow F2 of the ejector 202, and sucks the solid phase when sucked through the solid-phase suction pipe 205. The solid phase is accumulated in the collection container 204. FIG. 4 shows a pipe configuration from the solid phase suction pipe 205 to the ejector 202 via the collection container 204 and the solution suction pipe 206.

  In FIG. 1, the recovery route F <b> 4 for recovering the solid phase deposited on the bottom of the evaporator described as the fourth point is formed by a transfer pipe 209 that connects one end to the bottom of the collection container 204. In FIG. 1, reference numeral 210 denotes a valve for introducing the solid phase agitation fluid 212, and 211 denotes the next process equipment on the outlet side of the transfer pipe 209.

  As described above, in the first embodiment of the present invention, as shown in FIGS. 1 and 4, the mainstream F2 induction pipe 201, the ejector 202, the stirring nozzle 203, the collection container 204, and the like are configured. A valve 210 is installed in the mainstream F2 guide pipe 201. The collection container 204 includes at least one solid-phase suction tube 205. Further, the collection container 204 is connected to the ejector 202 and the solution suction pipe 206.

  Hereinafter, the collection and recovery processing by this configuration will be described. First, by opening the valve 210, the solid phase agitation fluid 212 flows into the ejector 202, the pressure inside the ejector 202 is reduced, and the solution 103 is sucked from the solution suction pipe 206 using the pressure difference from the evaporator 101 as a driving force. . A stirring flow F1, which is a mixed fluid of the solid phase stirring fluid 212 (F2) and the sucked solution 103 (F3), is jetted from the jet port 301 of the stirring nozzle 203, and the solid phase 105 deposited on the bottom of the evaporator 101 is obtained. Stir. The solid phase stirring fluid 212 is preferably a gas that does not chemically react with the solution. Vapor may be used when the dilution effect of the solution is negligible.

  As shown in FIG. 4, for example, when a collection container 204 having a donut shape and a circular cross section is used, the solid phase 105 can be stirred and collected without inhibiting the natural convection 104 in the evaporator 101. Further, by shifting the solid phase suction pipe 205 and the solution suction pipe 206 in the circumferential direction, the natural sedimentation distance of the solid phase 105 in the collection container 204 can be secured, and the separation amount of the solution 103 and the solid phase 105 is increased. Can be expected.

  Further, a transfer pipe 209 is connected to the collection container 204. After the concentration process, with the valve 210 closed, the solid phase 105 and the solution 103 collected from the transfer pipe 209 are sucked and transferred to the next processing process equipment 211. As a transfer method, the inside of the evaporator 101 may be pressurized, the solution 103 may be pushed out from the transfer pipe 209 and transferred to the next processing step equipment 211.

  FIG. 5 is a view showing a cross-sectional example of a collection container and a solid-phase suction pipe connected to the collection container. As shown in this figure, simultaneously with the drive of the ejector 202, the bottom of the evaporator 101 is connected via a collection container 204 connected to the solution suction pipe 206 and a solid-phase suction pipe 205 connected to the collection container 204. And the solid phase 105 diffused by stirring is sucked.

  The sucked solid phase 105 naturally settles by gravity in the collection container 204, and only the supernatant liquid is sucked into the ejector 202 through the solution suction pipe 206. By inserting the solid-phase suction tube 205 above the horizontal central axis 401 of the collection container, the amount of the collected solid phase 105 flowing out from the solid-phase suction tube 205 can be reduced.

  As described above, in the evaporator according to the present invention, the solid phase 105 that has been stirred and diffused simultaneously with the stirring can be collected, and the bottom of the evaporator can be maintained for a long time without reducing the operating rate of the evaporator 101. Life cycle cost reduction can be achieved by suppressing temperature rise and reducing evaporator corrosion potential. Further, by connecting the transfer pipe 209 to the collection container 204, the collected solid phase 105 can be transferred, and the maintenance cost can be reduced.

  In addition, FIG. 2 describes the case where there is heating from the outside of the evaporator 101 as an example. 1, 3, and 4 show an example, and shapes of an ejector 202, a collection container 204, a solid phase suction pipe 205, a solution suction pipe 206, a stirring nozzle 203, a transfer pipe 209, and an injection port 301 are illustrated. The position and quantity are not limited to this.

  In the second embodiment, as shown in FIG. 6, the solid phase suction pipe 205 is installed above the collection container 204, and the solid phase suction pipe 205 and the solution suction pipe 206 are shifted in the circumferential direction.

  By installing the solid-phase suction pipe 205 above the collection container 204, it is not necessary to insert the solid-phase suction pipe 205 into the collection container 204. Further, by adjusting the length of the solid phase suction pipe 205, the solid phase 105 scattered by stirring can be collected over a wide range in the vertical axis direction.

  Note that FIG. 6 shows an example, and the shapes, positions, and quantities of the collection container 204 and the solid phase suction pipe 205 are not limited thereto.

  In the third embodiment, as shown in FIG. 7, the solid-phase suction pipe 205 is installed below and above the collection container 204, and the solid-phase suction pipe 205 and the solution suction pipe 206 are shifted in the circumferential direction.

  By installing the solid phase suction pipe 205 below and above the collection container 204, the solid phase 105 deposited on the bottom of the evaporator 101 and the solid phase 105 scattered by stirring can be collected over a wide range. Further, by adjusting the length of the solid phase suction pipe 205, the solid phase 105 can be collected over a wide range in the vertical axis direction.

  About the solid-phase suction pipe 205 installed below the collection container 204, the backflow of the collected solid phase 105 can be prevented by inserting the solid-phase suction pipe 205 above the central axis of the collection container as in FIG. it can.

  FIG. 7 shows an example, and the shapes, positions, and quantities of the collection container 204 and the solid-phase suction pipe 205 are not limited to this.

  In Example 4, as shown in FIG. 8, the collection container 204 is installed at an angle from the horizontal axis.

  By setting the solution suction pipe 206 side to a high position and the transfer pipe 209 side to a low position, the amount of sedimentation of the collected solid phase 105 can be increased on the transfer pipe 209 side, and the solution 103 is transferred. In this case, the transfer amount of the collected solid phase 105 can be increased.

  FIG. 8 shows an example, and the shape, position, and quantity of the collection container 204 and the solid phase suction pipe 205 are not limited to this, and the angle of the collection container 204 from the horizontal axis is not limited.

DESCRIPTION OF SYMBOLS 101 ... Evaporator 102 ... External heater 103 ... Solution 104 ... Natural convection 105 ... Solid phase 201 ... Solid phase stirring fluid induction tube 202 ... Ejector 203 ... Stirring nozzle 204 ... Collection container 205 ... Solid phase suction tube 206 ... Solution suction pipe 209 ... Transfer pipe 210 ... Valve 211 ... Next process equipment 212 ... Solid phase stirring fluid F1 ... Stirring flow F2 ... Main flow F3 ... Collection flow F4 ... Recovery route 301 ... Injection port 401 ... Collection container Central axis

Claims (7)

The internal solution is heated by a heating mechanism such as a heater provided inside or outside, the solution is evaporated and concentrated, and the solution that precipitates a solid phase by concentration is targeted. In an evaporator that can be heated,
At the bottom of the evaporator, a collection container arranged to avoid the natural convection flow path due to the solution in the evaporator, and disposed toward the bottom of the evaporator, provided with an ejector in the middle, at the tip A guide pipe provided with an injection port; a first suction pipe provided in a part of the collection container for sucking the solution in the evaporator; and provided between the collection container and the ejector; A second suction pipe for guiding the solution in the collection container to the ejector,
The ejector joins the main flow introduced into the guide pipe and the collection flow obtained from the first suction pipe through the collection container and the second suction pipe, and jets the tip of the guide pipe An evaporating can characterized by being ejected as a stirring flow from the mouth to the bottom of the evaporating can. The evaporator according to claim 1,
An evaporator having one end connected to the bottom of the collection container and a transfer pipe for transporting the solid phase in the collection container to the outside of the evaporator. In the evaporator according to claim 1 or 2,
The evaporating can characterized in that the collection container disposed so as to avoid the natural convection flow path due to the solution in the evaporating can is constituted by a donut-shaped pipe. In the evaporator according to any one of claims 1 to 3,
The evaporator according to claim 1, wherein the first and second suction pipes are installed at different circumferential positions of the collection container constituted by a donut-shaped pipe. The evaporator according to claim 4,
The evaporator according to claim 1, wherein the first suction pipe is opened on a lower surface of the collection container, and the first suction pipe is inserted above the horizontal central axis of the collection container. In the evaporator according to claim 4 or 5,
The evaporator according to claim 1, wherein the first suction pipe is provided in an open state on an upper surface of the collection container. The evaporator according to any one of claims 3 to 6,
The collection container composed of donut-shaped piping is installed at an angle from a horizontal axis, and the second suction pipe is connected to the bottom of the lowermost part of the collection container. Evaporator can be characterized.

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